The present invention relates to a device for monitoring the circumferential speed of a toothed disc capable of being rotated, with a sensor arranged at a defined distance from the toothed rim of the toothed disc and with a sensor casing supported at and securable to a stationary guide member.
Such a device is known from the German patent specification 21 13 307. In the prior art the casing accommodating the sensor is guided in a slotted hole of a carrier element, with the sensor casing so being slidable within the slotted hole. Once the distance between the pole pieces and the toothed rim is established, the sensor casing is fixed by screw means within the guide so that an undesirable alteration of the distance is excluded. The distance between the toothed disc and the pole pieces of the sensor is adjusted by interposing between the said parts a plastic layer of defined thickness which is worn off in the course of the initial revolutions of the toothed disc.
In the described configuration, the distance between the sensor and the toothed rim of the toothed disc requires adjustment upon a removal of the sensor, which necessitates the availability of an adequate plastic layer of a defined thickness. On the other hand, the distance between the sensor and the toothed disc is adjusted by means of a guage, which is very time-consuming and may give rise to errors directly affecting the evaluation of the signals of the sensor.
Accordingly, the object of the present invention is to provide a device of the kind mentioned in the beginning in which adjustment of the sensor in the event of remounting is unnecessary.